A recent HowToGeek post called out Deep Roy as being the only actor to have appeared in all of the Star Wars, Star Trek, and Doctor Who franchises. A comment on that post mentions that Simon Pegg has also played characters in all those franchises but, since his Star Wars role was a voice-over, I believe this stretches the definition of "appeared" just a bit.

Another comment poses this question though, which I'm interested in having answered here:

Ah but are there any actors who have appeared in all three of the big Star **** franchises? Star Trek, Star Wars, and Stargate.

For the purposes of this question, "appeared" should be taken as "had an on-screen presence". That is to say, voice-overs don't count. Photographs or casual references made by other characters do not count either. The actor must have actually had a role, and been physically present in front of the camera, in a movie or TV production associated with each of the three Star-* franchises: Star Wars, Star Trek, and Stargate.

closed as not constructive by Flimzy, kalina, DForck42May 20 '13 at 13:40

As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by facts, references, or expertise, but this question will likely solicit debate, arguments, polling, or extended discussion. If you feel that this question can be improved and possibly reopened, visit the help center for guidance.
If this question can be reworded to fit the rules in the help center, please edit the question.

There's at least one I know of for Star Trek -> Star Gate (Saul Rubinek). Adding Star Wars is going to be harder - the other two were (very long running) TV series, with a larger need for 'guest stars' (heh).
–
Clockwork-MuseNov 26 '12 at 17:29

1

Wow. I should actually review my own links sometimes. From IMDB: "Along with George Takei, Clive Revill, Jason Wingreen, Felix Silla and Phil Fondacaro, he is one of only six actors to appear in both the "Star Wars" and "Star Trek" franchises." So, presuming that statement remains accurate, this question may just be: Have any of those six appeared in Stargate?
–
IsziNov 26 '12 at 18:37

2

Yeah, I'm not a big fan of these sort of questions. To me it's just a comparison of arbitrary lists.
–
DForck42Nov 26 '12 at 22:02

What about the fourth Star-franchise, -Search?
–
Tom Cody♦May 30 '13 at 10:51

Going by this link, there have been 8 people who've been on both Star Trek and Star Wars. This link, this link
and this give you the list of actors in stargate SG1 and Atlantis. Crossreferencing them hasn't given any hits so I'm afraid nobody made the crossover (and considering the current status of completion of all series, I don't think any will get the hattrick). I haven't gotten to the SGU list but I don't remember any familiar faces.

Thanks for the additional information on Trek/Wars crossovers. However, with the revival of the Star Wars and Star Trek movie franchises, there is still a possibility (albeit maybe remote) that someone from the Stargate franchise could end up with the "hat trick".
–
IsziNov 27 '12 at 13:44

true, let's hope so. I was more focused on Stargate and its status actually and didn't know if the question poster would accept the animated series
–
OriginNov 27 '12 at 15:04

Animated series would be a "no", since that would be outside the definition of "appeared in" (voiceovers don't count).
–
IsziNov 27 '12 at 15:42